ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 18

Document Title:

Pantex Plant – Site Description

Document Number: ORAUT-TKBS-0013-2 

Revision: 01

Effective Date: 07/27/2006

Type of Document: TBD

Supersedes: Revision 00

Subject Expert: Jerome B. Martin

Document Owner

Approval: Signature on File Approval Date: 06/01/2006

Jack J. Fix, TBD Team Leader

Approval: Signature on File Approval Date: 06/02/2006

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 06/01/2006

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 06/06/2006

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 07/27/2006

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 2 of 18

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

03/30/2004 00 New Technical Basis Document for the Pantex Plant – Site 

Description. First approved issue. Initiated by Jerome B. Martin.

07/27/2006 01 Constitutes a total rewrite of document. Revised as a result of the 

biennial document review. Incorporates NIOSH formal review 

comments. This revision results in no change to the assigned dose 

and no PER is required. Training required: As determined by the 

Task Manager. Initiated by Jerome B. Martin.
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 3 of 18

TABLE OF CONTENTS

SECTION TITLE

Acronyms and Abbreviations ...............................................................................................................

PAGE

4

2.1 Introduction ..............................................................................................................................5

2.2 Site Description........................................................................................................................6

2.3 Site Activities............................................................................................................................6

 2.3.1 Early Pantex Plant Operations ......................................................................................6

 2.3.2 Weapon Assembly and Disassembly Processes...........................................................7

2.4 Site Facilities............................................................................................................................9

 2.4.1 Bays............................................................................................................................10

 2.4.2 Cells............................................................................................................................11

 2.4.3 Special-Purpose Facilities ...........................................................................................13

 2.4.4 Nuclear Staging Facilities............................................................................................14

2.5 Pantex Radiation Protection Program .................................................................................... 14

2.6 General Radiation Exposure Characteristics.......................................................................... 15

References ........................................................................................................................................17

Glossary ............................................................................................................................................18

LIST OF FIGURES

FIGURE TITLE

2-1 Map of Pantex Plant.................................................................................................................

PAGE

6

2-2 Pantex nuclear weapon assembly process .............................................................................. 8

2-3 Weapons dismantlement and pit storage at Pantex Plant......................................................... 9

2-4 Generic representation of a nuclear explosive bay................................................................. 10

2-5 Generic representation of a nuclear explosive cell ................................................................. 12

2-6 Evolution of external dosimetry at Pantex and a cumulative plot of 

annual photon and neutron recorded dose............................................................................. 15
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 4 of 18

ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

CAM continuous air monitor

DOD U.S. Department of Defense

DOE U.S. Department of Energy

DU depleted uranium

EEOICPA Energy Employees Occupational Illness Compensation Program Act

FM farm-to-market

HE high explosives

hr hour

IFI in-flight insertable

IHE insensitive high explosives

lb pound

linac linear accelerator

MeV megaelectron-volt, 1 million electron volts

mm millimeter

mrad millirad

mrem millirem

NEOP nuclear explosive operating procedures

NDE nondestructive examination

NIOSH National Institute for Occupational Safety and Health

RAMS radiation alarm monitoring system

SNM Special Nuclear Material

TBD technical basis document

U.S.C. United States Code

yr year

§ section
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 5 of 18

2.1 INTRODUCTION

Technical basis documents and site profile documents are general working documents that provide 

guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. 

They will be revised in the event additional relevant information is obtained about the affected site(s). 

These documents may be used to assist the National Institute for Occupational Safety and Health 

(NIOSH) in the completion of the individual work required for each dose reconstruction.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy [DOE] facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act [EEOICPA; 42 U.S.C. § 7384l(5) and (12)]. 

EEOICPA defines a DOE facility as “any building, structure, or premise, including the grounds upon 

which such building, structure, or premise is located ... in which operations are, or have been, 

conducted by, or on behalf of, the Department of Energy (except for buildings, structures, premises, 

grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program)” [42 U.S.C. § 

7384l(12)]. Accordingly, except for the exclusion for the Naval Nuclear Propulsion Program noted 

above, any facility that performs or performed DOE operations of any nature whatsoever is a DOE 

facility encompassed by EEOICPA.

For employees of DOE or its contractors with cancer, the DOE facility definition only determines 

eligibility for a dose reconstruction, which is a prerequisite to a compensation decision (except for 

members of the Special Exposure Cohort). The compensation decision for cancer claimants is based 

on a section of the statute entitled “Exposure in the Performance of Duty.” That provision [42 U.S.C. § 

7384n(b)] says that an individual with cancer “shall be determined to have sustained that cancer in the 

performance of duty for purposes of the compensation program if, and only if, the cancer ... was at 

least as likely as not related to employment at the facility [where the employee worked], as 

determined in accordance with the POC [probability of causation1

As noted above, the statute includes a definition of a DOE facility that excludes “buildings, structures, 

premises, grounds, or operations covered by Executive Order No. 12344, dated February 1, 1982 (42 

U.S.C. 7158 note), pertaining to the Naval Nuclear Propulsion Program” [42 U.S.C. § 7384l(12)]. 

While this definition contains an exclusion with respect to the Naval Nuclear Propulsion Program, the 

section of EEOICPA that deals with the compensation decision for covered employees with cancer 

[i.e., 42 U.S.C. § 7384n(b), entitled “Exposure in the Performance of Duty”] does not contain such an 

exclusion. Therefore, the statute requires NIOSH to include all occupationally derived radiation 

exposures at the facility in its dose reconstructions for employees at DOE facilities, including radiation 

exposures related to the Naval Nuclear Propulsion Program. As a result, all internal and external 

dosimetry monitoring results are considered valid for use in dose reconstruction. No efforts are made 

to determine the eligibility of any fraction of total measured exposure for inclusion in dose 

reconstruction. NIOSH, however, does not consider the following exposures to be occupationally 

derived:

] guidelines established under 

subsection (c) ...” [42 U.S.C. § 7384n(b)]. Neither the statute nor the probability of causation 

guidelines (nor the dose reconstruction regulation) define “performance of duty” for DOE employees 

with a covered cancer or restrict the “duty” to nuclear weapons work.

• Radiation from naturally occurring radon present in conventional structures

• Radiation from diagnostic X-rays received in the treatment of work-related injuries

 

1 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC. 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 6 of 18

2.2 SITE DESCRIPTION

The Pantex Plant (Figure 2-1) is approximately 17 miles northeast of Amarillo in Carson County (in 

the Texas panhandle). The Plant site is bounded on the north by Texas Farm-to-Market (FM) Road 

293, on the east by FM 2373, and on the west by FM 683. To the south, DOE-owned property 

extends to within 1 mile of U.S. Highway 60. 

Figure 2-1. Map of Pantex Plant. 

The following discussions briefly describe Pantex Plant processes (Section 2.3) and facilities (Section 

2.4) and describe the origins of the associated radiological source terms. Section 2.5 describes the 

evolution of the Pantex radiation safety program. Section 2.6 summarizes the general characteristics 

of radiation exposure at Pantex. Dose reconstructors would use these data only if monitoring data 

were unavailable and other methods were not appropriate for dose reconstruction.

2.3 SITE ACTIVITIES

2.3.1

Pantex Plant was one of the last plants built during World War II to load, assemble, and pack 

ordnance. The plant began operations in September 1942 only 9 months after groundbreaking. By 

Early Pantex Plant Operations
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 7 of 18

the end of the War, Pantex had three loading lines running full time, which produced 500-lb bombs, 

105-mm howitzer shells, and 23-lb fragmentation bombs. Operations at Pantex stopped the week 

after the War ended on August 14, 1945 (Mitchell 2003). In 1951, when the U.S. Atomic Energy 

Commission (AEC) was looking for a new high explosives (HE) fabrication plant, the unused 6-yr-old 

HE loading line at Pantex was attractive. AEC contracted Silas Mason Company for the construction 

of 10 new buildings and modification of 3 others, and construction began on April 13, 1951 (Mitchell 

2003). Pantex completed its first HE operations in December 1951. By mid-1952, Pantex was at full 

production and was responsible for HE fabrication, assembly of nonnuclear components, retrofits, 

modifications, and disassembly for retirements. The 10 facilities included 6 Gravel Gertie cells and 

related explosives-manufacturing facilities that did not process Special Nuclear Material (SNM).

Beginning in 1948, the in-flight insertable (IFI) design was used in nuclear weapons. In this design, 

nuclear and nonnuclear components were kept separate until the time of use. The nuclear capsule 

did not require additional assembly, so military technicians could complete the final weapon assembly 

en route to the target by inserting the nuclear capsule into the mechanical assembly (Mitchell 2003). 

Between 1952 and 1954, the primary mission at Pantex was to precision-machine HE castings and 

send them to Sandia National Laboratory in Albuquerque, New Mexico, for assembly. From 1956 to 

1958, with the IFI design, the only nuclear components handled at Pantex were depleted uranium

(DU) cases and tritium reservoirs; during this time there was no processing of nuclear material (Martin 

2003a). Because these DU components were new at the time of assembly, this analysis assumed 

that removable DU oxide contamination on the components was minimal. In similar fashion, the 

potential for significant removable tritium contamination was minimal because the tritium reservoirs 

had to meet rigorous shipping requirements. The only other sources of radiation exposure at Pantex 

during this period were industrial radiography and medical X-rays.

In the late 1950s the sealed-pit design replaced the IFI design and delivery of sealed plutonium pits to 

Pantex became routine in 1958 (Mitchell 2003). New facilities were required for the sealed-pit design, 

which involved encapsulated SNM; six Gravel Gertie cells were completed in 1958. 

By 1966, all the older IFI weapons were dismantled, with most of the SNM recycled into the new 

sealed-pit weapons. In 1964, the weapon surveillance and repair mission was assigned to Pantex, 

while both Pantex and Burlington shared the retrofits and modifications mission. Pantex renovated 

facilities for HE development in the early 1960s and completed the separated-bay weapon assembly 

facility in 1970. Since 1975, Pantex has been the only DOE center for weapons assembly, 

disassembly, retrofit, and modification (Mitchell 2003). 

2.3.2

The nuclear weapon assembly process was highly standardized and consistent. Rigorous procedures 

were followed to ensure product quality and uniformity. Classified records documented every step of 

assembly and disassembly of every weapon including the badge number or inspection stamp of the 

person completing the step (Martin 2003b). With the advent of the sealed-pit design in 1958, all 

assembly and disassembly work was on complete sealed-pit weapons (Mitchell 2003).

Weapon Assembly and Disassembly Processes

Most parts for nuclear weapons assembly were manufactured within the nuclear weapons complex of 

government-owned/contractor-operated facilities. Pantex received those parts as completed major 

components (DOE 1997). These components supported one of three major processes: HE

subassembly, physics package assembly, or mechanical assembly. A process called palletizing

involved pulling the required parts for one weapon from warehouse stock into one or two large 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 8 of 18

baskets or pallets, which were delivered at the appropriate time to the bay or cell where assembly 

would take place (BWXT 2001).

The physics package operation involved the mating of the HE subassembly with the nuclear 

components. Once assembled into a single unit, the physics package was sent to the 

Non-Destructive Examination (NDE) section for radiography, then to Mechanical Assembly where the 

weapon was built around the physics package. The completed weapon was checked for leaks, which 

involved filling the weapon with a tracer gas such as helium or argon, placing the weapon in a vacuum 

chamber, and applying a vacuum in the chamber to detect any leaking tracer gas. Once the vacuum 

leak check was successfully completed, the interior of the weapon was purged and backfilled with an 

inert gas, usually nitrogen (BWXT 2001). 

The completed nuclear weapons, or warheads, were sent to the paint bay for touch-up painting. 

Warheads were sent to Mass Properties for spin balancing and to test moments and products of 

inertia and center of gravity. Once the mass properties procedures were complete, warheads were 

sent back to NDE for radiography. Bombs from the paint bay and warheads from radiography were 

both processed for ultimate user packaging, which included final checks on stenciling, serial numbers, 

and other program-specific documentation. Completed and packaged weapons were staged for 

shipment to the U.S. Department of Defense (DOD). 

Figure 2-2 is a schematic illustration of the weapon assembly process at Pantex. The shaded steps 

are those with the highest potential for radiation exposure. The following sections characterize the 

radiation source(s), the geometry of exposure situations, and the typical duration of exposures 

associated with these steps.

Figure 2-2. Pantex nuclear weapon assembly process (Mitchell 2003). 

Weapon Assembly Process

Completed HE 

Subassembly from 

Machining Process

Warehouse Received 

Parts & Components 

from Vendors

Palletized for:

• HE Subassembly

• Physics Package 

Assembly, or

• Mechanical 

Assembly

HE Subassembly, Pit, 

Secondary, & Palletized 

Parts Mated to Form 

Physics Package

Radiography

Physics Package 

to Mechanical 

Assembly Bay

Completed Weapon to 

Vacuum Leak Check

• Weapon Filled with 

Tracer Gas

• Weapon Placed in 

Vacuum Chamber

• Vacuum Pulled in 

Chamber

Weapon to Purge 

& Backfill

Warheads go to Mass 

Properties

• Spin Balance

• Moments & Products 

of Inertia

• Center of Gravity

Staging in

Zone 4

Back for New 

Material or 

Disassembly 

& Inspection

Shipped to DOD by Transportation 

Safeguards Division

Vacuum Leak 

Check or 

Weight Check

Pits & Components 

Received from 

Nuclear Weapons 

Complex

Bombs go To 

Paint Bay

Ultimate User 

Packaging

Warheads to 

Radiography
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 9 of 18

Figure 2-3 shows how the dismantlement of nuclear weapons at Pantex is basically the reverse of the 

assembly process. 

Figure 2-3. Weapons dismantlement and pit storage at Pantex Plant (Mitchell 2003). 

From 1951 to 1987, weapons were shipped between Pantex and DOD sites (primarily by rail in 

specially designed and built railcars) escorted by DOE couriers. From 1977 to the present, weapons 

have moved between Pantex and DOD sites in specially designed and built tractor-trailers, also 

escorted by DOE couriers (Mitchell 2003).

2.4 SITE FACILITIES

Figure 2-1 shows the location of the major Pantex Plant activities in Zone 4 and Zone 12. Major 

operations with radioactive materials included staging of SNM in Zone 4 and assembly and 

disassembly of nuclear weapons in Zone 12 South (BWXT 2001). 

The moderate-hazard facilities at Pantex are primarily those for assembly and disassembly and the 

special-purpose and nuclear staging facilities that have handled complete nuclear weapons (nuclear 

explosives) and components. The following sections describe the bays, cells, special-purpose 

facilities, and nuclear staging facilities at Pantex.
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 10 of 18

2.4.1

Figure 2-4 shows a generic bay situated off a ramp or hall for transport of a weapon or weapon 

component into the bay. The bay is accessed through a pair of interlocked blast-proof doors, which 

prevent one door from opening unless the other door is closed. A pair of double doors (also with an 

interlocking system) is used to bring equipment into the bay. A special work stand occupies the 

middle of the floor space for weapons work. Appropriate electrical, pneumatic, and safety alarm 

systems are permanently installed in the bay. In addition, an elaborate communication system is in 

place for monitoring the Nuclear Explosive Operating Procedures (NEOPs) and tracking the SNM. 

Redundant and diverse fire protection systems are in place, and strict control of combustible material 

is enforced. Certain operations require that the production technicians be electrically grounded to the 

weapon to avoid static discharge. In addition, operations are discontinued during lightning warnings 

(BWXT 2001).

Bays

Figure 2-4. Generic representation of a nuclear explosive bay

(Mitchell 2003). 

The principal function of the bays is the assembly and disassembly of nuclear explosives, particularly 

the mechanical portion, which includes the electrical components and tritium reservoirs (BWXT 2001). 

The major operations in these bays are the partial assembly or disassembly of nuclear weapons 

containing HE and the complete assembly and disassembly of nuclear weapons containing insensitive 

high explosives (IHE). 

Physics package assembly and disassembly, which involves bare pit and HE operations, take place in 

the cells. During the assembly process of a nuclear explosive, operations begin in an assembly cell 

and then move to an assembly bay for completion. The reverse is true for disassembly. Disassembly 

for HE weapons begins in a bay and concludes in a cell. Disassembly of weapons with IHE occurs 

only in a bay.
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 11 of 18

Alpha and beta continuous air monitors (CAMs) connected to the Pantex Radiation Alarm Monitoring 

System (RAMS) are used to detect airborne radiological contamination in the bays and cells (BWXT 

2001). The radiation safety system in the radiography bays provides interlocking safety devices to 

protect workers from accidental exposures. Additional safety measures include interlocks between 

the operating controls; gamma radiation detectors; panic switches; warning lights, chimes, and horns; 

passageway door switches; RAMS alarms; and fire alarms.

Nuclear explosives, nuclear components, radioisotopic thermoelectric generators, HE, and IHE are 

transferred to and from the bays using electric forklifts or manually operated transfer carts (BWXT 

2001). Only weapons containing IHE main charges can be completely assembled or disassembled in 

the bays. For pit-HE-IHE disassembly, employees wear lead-lined aprons, safety glasses, and vinyl 

gloves to handle bare pits. In addition, a safety net is used during pit-HE-IHE disassembly for some

operations. All assembly and disassembly operations are performed in the designated bay according 

to the written NEOPs and the Operations and Instructions Standards specific to a weapons program.

Radiographic inspections and certifications of nuclear explosive assemblies and subassemblies are 

performed in the radiography bays, which currently house an 8-MeV linear accelerator (linac) and a 

9-MeV linac (BWXT 2001). Each linac has the capability to examine completed nuclear explosives in 

addition to components and subassemblies. The radiography bays contain manipulator systems, 

turntables, alignment lasers, and closed-circuit television systems. The control room areas for the two 

radiography bays include a process/service room that provides development and processing of film 

from linac operations as well as film storage, viewing, and interpretation areas. In addition to the large 

fixed linac units, a portable X-ray machine can be used in the bays to radiograph pits. 

Process flow is similar in the two radiography bays (BWXT 2001). Assemblies are brought to the bay 

in fixtures that allow radiography, or they are removed and placed in suitable fixtures. The operator 

positions the film behind the unit, perpendicular to the beam in relation to the linac and the unit. 

During operation of the linac, the operator moves to the control room to make the radiographic 

exposure. All personnel remain in the control room during the exposure. There are numerous 

emergency stop switches on the walls inside the radiography bays, which disable or prevent the 

operation of the radiography equipment in the event personnel are accidentally trapped in the bay. 

The control room is isolated from the linac room such that exposure rates to personnel follow as low 

as reasonably achievable principles and do not exceed 0.25 mrem/hr. During operation of the 

portable unit, the operator would occupy the vestibule portion of the bay where exposure rates to 

personnel do not exceed 0.25 mrem/hr. The portable X-ray machine is operated via a control console 

connected to it by cables. The operator, after making the radiographic exposure, develops the film in 

the process/service room. The operator views the film, makes the appropriate verifications of internal 

structure, and completes the necessary forms to release the unit for work by other departments.

The generic-use bays in these buildings can be configured for staging operations. Weapons and 

components are held in staging bays in preparation for use in assembly, special testing, or 

transportation off the site. 

2.4.2

The mounded earth and gravel cover over a cell is supported by a cable catenary system. The cables 

are suspended from the top of a cell's round room wall. The cell roof consists of the support cables, 

layers of wire mesh, gravel and earth coverings, and a Gunite or concrete cap. Figure 2-5 shows a 

generic cell design from Mitchell (2003).

Cells
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 12 of 18

The design of the cells is based on Gravel Gertie experiments that show that the structure largely 

dissipates blast pressures (BWXT 2001). The mounded gravel roof over the round room is designed 

to lift and vent gas pressures produced in an accidental explosion. Plutonium would be filtered from 

the vented gases by the gravel material and release to the environment would be minimized. The 

equipment passageway doors are designed to remain intact in the event of accidental detonation, and 

the doors are interlocked so only one door can be open at a time. The two blast doors are also 

interlocked.

Figure 2-5. Generic representation of a nuclear explosive cell. 

Source: Mitchell (2003)

The cell facilities consist of a round room, staging cubicles, a corridor area, and an 

equipment/mechanical room. All of these areas are inside the blast-resistant cell structure and are 

protected from external events, including external explosions, winds, and tornados. The principal 

function of the cells is the assembly and disassembly of nuclear explosives, particularly operations on 

the physics packages of nuclear explosives that contain HE (BWXT 2001). Work on nuclear 

explosives that contain IHE can be done in the bays. In the future, most of the operations in the cells 

are expected to involve the dismantlement of retired stockpile weapons.

The cells were designed as assembly/disassembly and inspection areas with the capability to process 

HE and nuclear explosive components that contain plutonium (BWXT 2001). The major operations 

are pit-HE assembly, pit-HE disassembly, and complete nuclear explosive assembly and 

disassembly. A number of specialized operations support quality assurance for these activities.

To comply with DOE and Pantex Plant requirements, plutonium-HE assembly and disassembly 

operations must be conducted in a cell-type structure where the design features of the facility afford 

an added margin of safety (DOE 2001). Partial assembly can be performed in a cell to the point 

where the HE component is considered cased. In this configuration, completion of the assembly 

process is typically performed in the bay facilities.

Components for a particular weapon are sent to the operating cell performing the assembly (BWXT 

2001). Assembly operations are performed in designated cells according to NEOPs and other written 

procedures specific to a nuclear weapons program. Inspections and audits are performed to confirm 

that design specifications are met. Acceptance inspections are performed by DOE inspectors. During 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 13 of 18

all phases of assembly, procedures specific to nuclear explosives are followed and checklists are 

initialed as each procedural step is completed. Once the nuclear explosive assembly is complete, it is 

sent to radiography (if required) to verify the presence of SNM and to confirm the position of the safing 

device. If required, the weapon is then sent to the vacuum chambers for final inspection and testing. 

During a limited (or partial) assembly, pits are transferred to the cells from the designated SNM 

staging facility at Pantex Plant. HE comes from an in-process staging facility for HE. Partial 

assembly in a cell typically results in a cased nuclear explosive assembly containing a pit mated with 

HE, which is then sent to an assembly bay facility for final assembly into a nuclear explosive.

Cells are also used extensively for the disassembly or partial disassembly of nuclear explosives that 

have been returned to DOE by DOD (BWXT 2001). Many of these nuclear explosives were designed 

and built without the added safety benefit of IHE. Therefore, disassembly operations must be 

completed in a cell after other component disassembly operations have been completed in other 

facilities.

Plutonium pit-HE assemblies are brought to the cells from other facilities in Zone 12 (BWXT 2001). 

Special tools and equipment are supplied from warehouse stocks. Some disassembly operations 

require a portable glovebox or other specialized equipment. For plutonium pit-HE disassembly, 

personnel must use a safety net, safety latches, special tooling, lead aprons, safety glasses, and 

approved gloves. Some operations require that portions of the round room floor be covered with a 

barrier paper taped to the floor. In the event of an accident or unanticipated contamination, this 

barrier paper can be peeled from the floor and disposed of as contaminated waste, which aids 

containment and cleanup. 

During disassembly, suspect components must be checked for radioactive contamination. If 

components are contaminated, decontamination procedures are performed before the components 

are transported.

2.4.3

The special-purpose facilities at Pantex include the Paint Facility, the Separation Testing Facility, the 

Mass Properties Facility, the Weapons Aging Facility, and the Weapons Transfer Station (BWXT 

2001).

Special-Purpose Facilities

The Paint Facility is used to spray-paint weapons, components, and supporting container and 

transportation hardware. Radiation exposure rates to workers in the Paint Facility are comparable to 

those of transportation workers who move weapons containing nuclear materials, which are typically 

less than 100 mrem/yr. The Paint Facility is restricted to Nuclear Explosive Look-Alike assemblies. 

The presence of HE (or IHE) and SNM at the same time is not allowed in the paint bay.

Operations in the Separation Testing Facility involve functional separation tests of selected reentry 

body assemblies, which is a continuing requirement of the Weapons Surveillance Program. 

Separation tests are conducted remotely with authorized personnel in the control booth during the 

entire test. Worker exposures to the weapons at the beginning and end of each test are brief, and 

cumulative radiation exposures are typically less than 100 mrem/yr. 

The Mass Properties Facility utilizes two bays and a remote control room. One of the bays has a 

spin-balancing machine that works much like a machine for balancing automobile tires. The weapon 

is placed in the machine and spun to measure any out-of-balance forces. The correct placing of 

balance weights on the weapon is determined from the results of the test. The center of gravity of the 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 14 of 18

weapon and the moment and product of inertia of the weapon are measured in another bay. Worker 

exposures to the weapons at the beginning and end of each test are brief, and cumulative radiation 

exposures are typically less than 100 mrem/yr.

The Weapons Aging Facility places the weapon or related component in an enclave that controls the 

temperature in the enclave such that the weapons and components are aged artificially over an 

accelerated timeframe. As in the case of the Mass Properties and Separation Test Facilities, the 

operations are observed and controlled from a remote control room. Worker exposures to the 

weapons at the beginning and end of each test are brief, and cumulative radiation exposures are 

typically less than 100 mrem/yr. 

The Weapons Transfer Station is used for loading and unloading weapons, components, and

explosives. It is a completely enclosed high dock that accommodates over-the-road trailers and 

forklifts. 

2.4.4

Zone 4 facilities are for staging or interim storage for weapons, components, and other 

process-related materials (BWXT 2001). Periodic inspection of the pits is required; process 

technicians accompanied by radiation safety technicians perform this operation. Personnel are 

exposed isotropically to radiation sources during this work.

Nuclear Staging Facilities

Zone 12 staging facilities, including pit vaults, warehouses, and SNM component staging facilities, are 

where nuclear explosive components without HE are staged (BWXT 2001), including pits, 

radioisotopic thermal generators, and tritium reservoirs. Pits are encapsulated components packaged 

in specially designed containers for staging and transportation between facilities. Radioisotopic

thermal generators are small, self-contained, sealed 238Pu sources of thermally generated electricity. 

Tritium reservoirs are small metal bottles filled with tritium gas. 

2.5 PANTEX RADIATION PROTECTION PROGRAM

The radiation protection program at Pantex evolved gradually over time, with a major expansion after 

a tritium release incident in May 1989. A radiation dosimetry program was established at Pantex in 

1952 by the manager of the radiography group. The technology of the program has evolved over the 

past 50 yr from simple film badges to sophisticated thermoluminescent dosimeter systems. 

Figure 2-6 shows the steps in the evolution and a cumulative plot of annual photon and neutron 

recorded dose. Technical Basis Document for the Pantex Plant – Occupational External Dosimetry

(ORAUT 2004a) describes these steps in detail. The records of radiation doses to individual workers 

from personnel dosimeters represent the highest quality records for retrospective dose assessments. 

The radiation protection program was focused on those most likely to be exposed to radiation: 

Production technicians, material handlers, transportation workers, radiography technicians, quality 

control technicians, and warehouse production workers. ORAUT (2004a) describes these workers 

and their exposure potentials. All other workers at Pantex had little occasion to enter radiological 

areas, and their potential for radiation exposure or intakes of radioactive material is considerably less.

From 1951 to about 1980, nuclear weapons assembly operations were generally free of 

contamination. Occasional checks for removable contamination generally demonstrated negative 

results, so few precautions were taken in relation to personal protective equipment and clothing. 

There was no evidence of any intakes of radioactive materials by Pantex workers. The major 

emphasis was on monitoring external radiation exposure by the methods shown in Figure 2-6. 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 15 of 18

In 1972, a modest bioassay program was begun for monitoring worker exposures to tritium; in 1976, 

the program was expanded for a 4-yr period with generally negative results. In the early 1980s, with 

the increasing disassembly of weapons that had been in various environments, DU contamination 

became a greater concern and additional radiation protection measures were applied to 

contamination control. In 1988, an extensive bioassay program for workers exposed to DU 

Pantex Cumulative Annual Doses

0

500

1000

1500

2000

2500

1950 1960 1970 1980 1990 2000

Year

Cumulative Dose, person-rem

Neutron

Photon

TLND

TLD

809/812

802

Film

NTA

Figure 2-6. Evolution of external dosimetry at Pantex and a cumulative plot of 

annual photon and neutron recorded dose. 

contamination was implemented. Technical Basis Document for the Pantex Plant – Occupational 

Internal Dose (ORAUT 2004b) describes the bioassay programs in detail.

Airborne contamination is monitored with alpha CAMs and tritium monitors. The air monitoring 

system was installed in the early to mid-1970s. The alpha CAM system frequently responds to 

elevated radon concentrations, but has rarely detected airborne concentrations of uranium, thorium, 

or plutonium. The tritium monitors frequently respond to minor local releases of tritium gas. The few 

occasions when airborne contamination has been detected are documented in incident reports as 

described in ORAUT (2004b). 

Following the tritium release incident in May 1989, the radiation protection program expanded rapidly. 

In May 1989 there were only seven staff members in the Radiation Safety Department; by mid-1991 

the staff had expanded to 50 and new facilities and modern equipment were added. 

2.6 GENERAL RADIATION EXPOSURE CHARACTERISTICS

The general radioactive source terms have been consistent throughout the history of Pantex, with few 

exceptions. From 1951 to the present, DU and tritium have been present at Pantex. During 

assembly, the DU was relatively clean and there was minimal removable contamination. The tritium 

was received in sealed reservoirs, and leakage was not a concern during assembly. Minor leakage 

occurred during disassembly. From 1958 to the present, sealed plutonium pits and enriched uranium 

components have been received, handled, and stored at Pantex. With two minor exceptions, 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 16 of 18

plutonium has always been contained by the pit cladding. Some thorium components were 

assembled into weapons in the 1960s and disassembled during the 1990s. These source terms are 

approximately the same for Zones 4 and 12. There are, and have been, a few other radioactive 

materials present in small quantities as calibration sources or in larger quantities as radiography 

sources. ORAUT (2004a) discusses those source terms in more detail. 

Radiation exposures occur at Pantex when workers are involved in operations with radioactive 

materials, such as the assembly or disassembly of nuclear weapons. The primary sources of external 

radiation exposure are plutonium pits and DU or thorium components. The primary sources of 

radioactive contamination (which can lead to intake) are DU oxide and tritium.

Plutonium pits are sealed to prevent surface contamination problems. Enriched uranium components 

are solid, hermetically sealed units. The pits emit the X-rays, gamma rays, and neutrons that are the 

major source of exposure to Pantex radiation workers. Direct handling of pits can result in relatively 

high dose rates. Workers wear lead aprons during pit-handling work, which substantially reduce lowenergy photon doses to the torso. Dosimeters are usually worn under the lead apron, which captures 

the reduced torso dose but underestimates the dose to the head including the thyroid and eye lens 

doses. Neutron doses measured under the lead apron can be underestimated. Beta and photon 

exposures occur during handling of DU or thorium components. The rule-of-thumb beta dose rate of 

approximately 200 mrad/hr at the surface of a DU slab can be used to estimate worker exposures. 

Exposures to thorium include penetrating 2.6-MeV photons from 208Tl. 

The major radioactive contamination concern is DU oxide during disassembly operations. DU 

components tend to oxidize while in the field, and this oxide is present as a readily dispersible powder

during disassembly. ORAUT (2004b) discusses this contaminant. Contamination on thorium 

components is much less significant. In addition, tritium contamination is a concern; minor tritium 

intakes occur routinely but with very little whole-body dose. The one exception is the Cell 1 incident in 

1989, which is discussed in detail in ORAUT (2004b). 
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 17 of 18

REFERENCES

BWXT (Babcock & Wilcox Technologies, Inc.), 2001, Safety Information Document in Support of the 

National Environmental Policy Act Documents for Pantex Plant, Amarillo, Texas. [This 

document contains Unclassified Controlled Nuclear Information (UCNI).]

DOE (U.S. Department of Energy), 1997, Linking Legacies: Connecting the Cold War Nuclear 

Weapons Production Processes to Their Environmental Consequences, DOE/EM-0319, Office 

of Environmental Management, Washington, D.C., January.

DOE (U.S. Department of Energy), 2001, Safety of Nuclear Explosive Operations, DOE Order 452.2B, 

Washington, D.C., August 7.

Martin, J. B., 2003a, "Personal communication with Bob Carr," memorandum to file, September 24, 

Oak Ridge Associated Universities Team, Oak Ridge, Tennessee.

Martin, J. B., 2003b, "Personal communication with Edward E. Poore," memorandum to file, 

September 24, Oak Ridge Associated Universities Team, Oak Ridge, Tennessee.

Mitchell, K. C., 2003, Rhetoric to Reality: A Cold War Context Statement for the Pantex Plant, 1951-

1991, BWXT Pantex LLC, Amarillo, Texas.

ORAUT (Oak Ridge Associated Universities Team), 2004a, Technical Basis Document for the Pantex 

Plant – Occupational External Dosimetry, ORAUT-TKBS-0013-6, Rev. 00-E, Oak Ridge, 

Tennessee.

ORAUT (Oak Ridge Associated Universities Team), 2004b, Technical Basis Document for the Pantex 

Plant – Occupational Internal Dose, ORAUT-TKBS-0013-5, Rev. 00-F, Oak Ridge, 

Tennessee.
Document No. ORAUT-TKBS-0013-2 Revision No. 01 Effective Date: 07/27/2006 Page 18 of 18

GLOSSARY

depleted uranium (DU) 

Uranium with a percentage of 235U lower than the 0.7% found in natural uranium. As 

examples, spent (used) fuel elements, byproduct tails, residues from uranium isotope 

separation, and some weapons materials contain DU. DU can be blended with highly 

enriched uranium to make reactor fuel or used as a raw material to produce plutonium.

Gravel Gertie 

Facility covered with crushed gravel to contain radioactive contamination from the potential 

accidental explosion of a nuclear weapon during assembly or disassembly, characterized by a 

cable-supported roof of wire mesh and a thick gravel overburden. Also called Gertie. 

high explosive (HE) 

Chemical compound or mechanical mixture that, when subjected to heat, impact, friction, 

shock, or other initiation stimulus, undergoes a rapid chemical change resulting in large 

volumes of highly heated gases that exert pressure in the surrounding medium. See 

insensitive high explosive. 

insensitive high explosive (IHE) 

High explosive that is so insensitive that there is negligible probability of accidental initiation or 

transition from burning to detonation. See high explosive. 

nuclear explosive look-alike assembly 

At Pantex, model of the basic configuration of a nuclear explosive that does not contain 

radioactive material.

pit 

Package at the center of an implosion weapon that contains the machined fissile material that 

begins the fission chain reaction. Also called primary.

Special Nuclear Material (SNM) 

Plutonium or uranium enriched to a higher-than-natural assay including 239Pu, 233U, uranium 

containing more than the natural abundance of 235U, or any material artificially enriched in one 

of these isotopes.

tritium reservoirs 

Gas-tight metal containers for storage of store tritium gas.